Fiber-optic telecommunication networks are constantly being upgraded to carry more and more channels over a single optical fiber. And while fiber manufacturers may not applaud this trend because it decreases the demand for optical fiber, it clearly signals the direction of this industry. Indeed, Lucent Technologies Inc. recently announced an optical system having over 100 channels, each transmitting 10 gigabits of data at a different wavelength, over a distance of nearly 250 miles (400 km) using its TrueWave.RTM. fiber. This represented the world's first long-distance, error-free transmission of a terabit (1 trillion bits) of information per second over a single strand of optical fiber. Associated with such multi-channel optical systems are wavelength division multiplexers (WDM), which operate to combine an number of separate and distinct wavelength regions (channels) onto a single optical fiber in one direction of transmission, and to separate them from the optical fiber in the other. This is to say that the WDM operates as multiplexer in one direction of transmission, and as a demultiplexer in the other. These channels each have a different central wavelength (i.e., .lambda..sub.1, .lambda..sub.2, . . . .lambda..sub.n) and, for optimum performance of the WDMs and associated transmitters and receivers, it is important that the optical signal power of each channel be precisely controlled, and preferably equal to all others.
It is desirable to have a common structure, which can be installed in individual ports of an optical multiplexer and/or an optical demultiplexer, and used to control the power level of optical signals. At one end, this structure would be shaped to fit into a jack connector as though it were a standard optical plug connector. At the other end, this structure would be shaped to receive a standard optical plug connector. Accordingly, whenever it is desirable to add attenuation (i.e., insertion loss), for example, to an optical path, this structure is interposed between a standard optical plug connector and a standard optical jack connector. Such a structure is referred to as an "optical adapter" herein.
Optical adapters exist that include attenuators, but they are somewhat expensive because they have an abundance of parts, many of them machined, and these parts must be manually assembled. Such adapters are presently available for use in connection with FC, SC and ST optical connectors. However, these adapters were developed when competitive cost pressures were minimal and customers would gladly pay any price to have them, which is no longer the situation.
A new optical connector, designated "LC," has been developed with a ferrule having a diameter that is only 1.25 mm, which is half the diameter of the above-mentioned FC, SC and ST connectors. More importantly, the LC connector uses a cantilever latch during interconnection with a mating connector in a manner similar to the modular plugs and jacks used in conventional telephone equipment. At the present time, there are no suitable adapters for use with LC connectors.
In addition to providing the attenuation function, the same adapter structure should accommodate other functions such as interconnecting ferrules of different sizes or interconnecting connectors of different styles.
Accordingly, what is desired is an optical adapter that can be used in various applications and to have a small number of parts so that it can be assembled with relative ease. Further, it is desirable for the adapter to work with LC-type connectors.